1 million cells for TCF1 ChIPseq were sorted (gd+, CD24+ and CFPhi or CFPlo/-), crosslinked with 1% formaldehyde, sonicated, and then subjected to chromatin immunoprecipitation with anti-TCF1 antibody. 300-500 bp DNA fragments were obtained after reverse-cross linking. 1 million cells of DP were isolated from C57BL/6 thymocytes. The TCF1 ChIP DNA fragments were processed for ChIPseq with Illumina adapters and Illumina primers (Primer1.1 and Primer2.1). After adapter ligation, DNAs were PCR-amplified for 17 cycles and library fragments of 300-500 bp were extracted from an agarose gel.